"The take-home message is that you can eat well during your pregnancy without overeating, and pregnancy should not be a license to overeat, and pregnancy should not be a contributing factor to the epidemic of obesity in this country," researcher Yvonne S. Thornton, MD, MPH, tells WebMD.

Thornton's findings, published in the June edition of the Journal of the National Medical Association, go further than the Institute of Medicine (IOM) did in its new guidelines for pregnancy weight.

The IOM recommends that obese women gain 11-20 pounds during pregnancy. Thornton's team argues that obese women may have healthy pregnancies maintaining their weight, provided they have professional nutritional guidance -- and accountability about what they eat.

Pregnancy "is not a time to eat twice as much, but twice as well," Thornton says.

Pregnancy Weight Study

Thornton's study included 232 New York state women who were obese when they got pregnant. The women's BMI (body mass index) ranged from 30 to 69, averaging in the upper 30s.

All of the women got information about nutrition during pregnancy. Half of the women also got a personalized healthy eating program and kept food diaries, which were reviewed at each prenatal checkup. For comparison, the other half of the group didn't get eating plans and didn't keep food diaries.

Thornton says she deliberately didn't use the word "diet" because she considers it "an emotionally charged word" and because the study wasn't about losing weight during pregnancy.